Other tools have been developed for reshaping and restoring damaged or deformed tubular stock, such as the piping of automobile type exhaust systems, as shown in my prior U.S. Pat. No. 3,324,701. One of the disadvantages associated with the tool described in my prior U.S. Pat. No. 3,324,701 is that a threaded handle has to be turned in order to expand a plurality of expandable segments prior to forcing the expandable segments into tubular stock for reshaping the tubular stock. The expandable segments are set initially to a desired diameter by axial movement of a wedge or cam member threaded to a central spindle or shaft. The stock is reshaped by forcing the expanded segments, having tapered leading edges, into the stock and then removing the tool, further expanding the segments, and again forcing the segments into the stock to further reshape the interior of the stock by means of a hammer blow applied to the handle of the tool. The repeated removal and expanding of the device as well as the cumbersome wedge extending from the insertion end of the device makes its use very difficult.
Another disadvantage of U.S. Pat. No. 3,324,701 is that the spreader segments can become misaligned axially with each other during tubular expansion since there is no means to prevent the individual spreader segments from sliding axially on the cam. Lack of axial alignment adversely affects the uniformity of the tubular stock expansion because the cross-sectional geometry of the expanded mandrel becomes less like a circle when the segments are misaligned. The cross-sectional geometry of the mandrel during expansion determines the final cross-sectional geometry of the tubular stock that is expanded. Thus, axially misaligned spreader segments can result in tubular stock being expanded into substantially non-circular and somewhat unpredictable cross-sections.
U.S. Pat. No. 4,753,101 overcomes the disadvantage of the threaded handle that had to be turned; however, it still requires an impact to the wedge for the segments to expand radially. Furthermore, it too has the disadvantage of spreader segments becoming axially misaligned during tubular expansion, causing substantially non-circular expansion of the tubular stock. Also, upon maximum expansion, subsequent impacts or shocks caused a transfer of axial force from the cam member flange directly into spreader segment flanges at an end edge of the mouth of tubular stock. This resulted in axial misshaping of the tubular stock mouth from the axial forces.
Another tool, shown in FIG. 1, accomplishes tubular stock expansion without an axial impact by means of a hammer or the like. In that tool a bolt 1 runs through the hollow center of an internally threaded cam 5. Cam 5 is placed inside tubular stock 32, with the narrow end 7 of cam 5 facing mouth 135 of tubular stock 32. When bolt 1 is rotated, cam 5 is drawn by bolt 1 toward mouth 135 of tubular stock 32. Since cam 5 is shaped as a wedge, with its narrow end 7 facing mouth 135 of the tubular stock 32 to be widened, mandrel 13, comprised of 4 segments 20, receives a radial force when bolt 1 draws cam 5 toward mouth 135 of tubular stock 32. This tool, however, also has the disadvantage of spreader segments 20 becoming axially misaligned with each other, causing the final geometry of the tubular cross-section to be substantially non-circular. This results from lack of any axial alignment means associated with the forward, mandrel-insertion ends 23 of the spreader segments 20.
Another disadvantage is that the amount which tubular stock 32 can be widened is limited by the tubular stock's diameter d1. This is so, because cam 5 must fit inside tubular stock 32 and the dimensions of cam 5 determine the amount of tubular expansion which can occur.
A disadvantage shared by some of the prior art is that a tap on the outside of the tubular stock is required for removal of the device from the tubular stock upon completion of tubular stock expansion. The device of the present invention can be removed smoothly from the tubular stock, without a tap, upon completion of expansion.